Problem: A rectangle has area $48\mbox{ cm}^2$, and its length is three times its width. What is the perimeter of the rectangle, in centimeters?
Solution: Let the width be $w$ cm. Then $(3w)w = 48$, so $w = 4$. So, the perimeter in centimeters is $2\cdot 4 + 2\cdot (3\cdot 4) = 8 + 24 = \boxed{32}$.